Geoscience Reference
In-Depth Information
becomes cosmochemistry. The main evidence of the chemical
composition of extraterrestrial bodies is provided by meteorites that
regularly fall to Earth. The only other physical samples of celestial
bodies in our possession are those collected from the Moon by
astronauts in the seven Apollo missions (USA) from 1969 to 1972,
and those collected by automatic probes that have brought samples
back to Earth, i.e. Luna 16 (Soviet Union) which landed on the Moon
in 1970 and Stardust (USA)
above the comet Wild 2 in 2004, which
brought dust samples back to Earth in 2006. Other probes returning
samples from other extraterrestrial bodies back to Earth are expected
over the next few decades. In addition, there may be human
expeditions to the Moon or Mars.
Abbreviation
Definition
Anammox
Anaerobic ammonium oxidation
DIC
Dissolved inorganic carbon
PIC
Particulate inorganic carbon
OMZ
Oxygen minimum zone
pCO
2
Partial pressure of CO
2
UV
Ultraviolet radiation
∑CO
2
Total CO
2
or DIC (equation [4.2])
Table 4.1.
Abbreviations and special symbols used in this chapter
Earth's crust
Seawater
Atmosphere
Element
%
Element
%
Element
%
Oxygen (O)
46
Oxygen (O)
86
Nitrogen (N)
75
Silicon (Si)
28
Hydrogen (H)
11
Oxygen (O)
23
Aluminum (Al)
8.1
Chlorine (Cl)
1.9
Argon (Ar)
1.3
Iron (Fe)
5.0
Sodium (Na)
1.1
Carbon dioxide (CO
2
)
<0.1
Table 4.2.
Names and percentages by mass of the four main chemical elements
present in three major geochemical reservoirs that form the main outer envelopes of
the Earth (i.e. the Earth's crust, the seawater and the atmosphere)
C
OMMENTS ON
T
ABLE
4.2.- The percentage given for each element is
the fraction of the mass of that element in the total mass of
the reservoir. For the atmosphere, each value takes into account the
density of the gas and the air at normal temperature and pressure
(20°C, 1 atm). In many geochemistry textbooks, the percentages cited
